To be completely frank, I never actually thought any of these things were bad things to say! Some of these things, actually seem like compliments to me, no?! At the same time, if I think about it more and more, I start to realize that they may have a negative effect that we do not intend.
1. "You're so much better than all the other jerks I've dated." -> Who wants to be compared to anyone? If my bf told me "you are so much better than every other girl," the crazy side of me may think "better in what way," "does he still think about his exes?" If I can see myself thinking that, then perhaps he will too no?
2. "Can you really afford that?'' -> I have heard my parents say this to me, and it has ticked me off! Now that I think about it, it would tick me off even more if my bf said this to me! I apologize :(
3. "So we're running a little late. Relax." -> See this one is hard for me to understand. If we are a little late, what will happen? Nothing. But the issue is that my guy friends have all told me that this is really one of girl quotes that irks them the most.
4. "He's a great guy — you should be friends with him." -> Ok, ladies, this is definitely a no-no. We may not want to admit it, but the male ego is so fragile. It is almost like a glass door, and even the smallest pebble may shatter it. Of course, this could get him thinking "oh so you could go for him?", so why take the risk?
5. "She made me promise not to tell, but..."
6. "Don't be silly — I haven't done that in ages." -> This is a huge no-no! This means that you were willing to do things with another guy or before that you are not willing to do with him! This can make him think all types of things.
As a rule of thumb, ladies, I advise all of you to think "what would I feel if he said that to me." That is really the only and best way to avoid misunderstandings. Of course, not all of them could be avoided, but we can try!

Oh, yeah. I'm sure these have been said for sure. I've always heard you should never say the first one. I remember it being that no one wants to be compared to others you've had, especially since it seems that the person saying a line like that, would compare all the time.